Modern silviculture often requires the planting of large numbers of genetically identical plants that have been selected to have advantageous properties. Production of new plants by sexual reproduction, which yields botanic seeds, is usually not feasible. Asexual propagation, via the culturing of somatic or zygotic embryos, has been shown for some species to yield large numbers of genetically identical embryos, each having the capacity to develop into a normal plant.
Somatic cloning is the process of creating genetically identical plants from plant tissue other than male and female gametes. In one approach to somatic cloning, plant tissue is cultured in an initiation medium that includes hormones, such as auxins and/or cytokinins, to initiate formation of embryogenic tissue, such as embryogenic suspensor masses, that are capable of developing into somatic embryos. The embryogenic tissue is then further cultured in a multiplication medium that promotes multiplication and mass production of the embryogenic tissue. The embryogenic tissue is then cultured in a development medium that promotes development and maturation of cotyledonary somatic embryos that may, for example, be placed on germination medium to produce germinants, and subsequently transferred to soil for further growth, or alternatively, placed within manufactured seeds and sown in soil where they germinate to yield seedlings. Manufactured seeds are described, for example, in U.S. Pat. Nos. 5,564,224; 5,687,504; 5,701,699; and 6,119,395.
The somatic embryogenesis process typically is laborious and inefficient. For example, a labor intensive step in the embryogenesis process is the selective harvesting from development medium of individual embryos suitable for germination.
Efforts have been made to automate the harvesting of cotyledonary embryos. One of the steps in the harvesting process is known as separation. At the end of the development phase, the embryos may be present in a number of stages of maturity and development, and are typically attached to or imbedded in embryogenic suspensor mass. Separation is a processing step that occurs at the end of development and maturation in which plant embryos are physically separated from each other and the underlying embryogenic suspensor mass (ESM) before further processing such as, for example, insertion into manufactured seed, or placement onto germination or pre-germination medium for further treatment prior to insertion into manufactured seed. Separation may be accomplished by spraying the embryos and attached ESM with liquid to remove the embryos from the development medium and using a series of sieves to separate the embryos from each other and residual ESM.
The present invention is directed to a spray apparatus and methods for separating plant embryos